DE10159697B4 - Redundant facilities in a process control system - Google Patents

Abstract

A process control system for communication in a process control network comprising a plurality of redundant virtual I / O devices (130) each having a unique address, the process control system comprising: a bus (110); a redundant master (120) of the virtual I / O device (130) having a first unique address, communicatively connected to the bus (110) and programmed to publish messages on the bus having a virtual publish address , and having a publication buffer (132) and a subscriber buffer (134); a redundant secondary device (122) of the virtual I / O device (130) having a second unique address communicatively connected to the bus and programmed to publish messages on the bus having the virtual publish address and with a publication buffer (136) and a subscriber buffer (138); and at least one receiving device communicatively connected to the bus and programmed to process messages published on the bus having the virtual publication address of the virtual I / O device; wherein the bus (110) is connected to the main device (120), to the secondary device (122) and to at least one receiving device, and wherein the redundant main device (120) operates in an active mode in which the redundant main device (120) messages transmits on the bus (110) for at least one receiving device, and the redundant secondary device (122) operates in a standby mode in which the secondary device (122) does not transmit messages on the bus, and wherein the publication buffer (136) of the secondary device (122) stores messages of the main facility (120) received in the reserve mode.

Description

The present invention relates generally to process control networks, and more particularly to a process control system and method and apparatus for implementing redundant devices in a process control network.

Process control networks of the type discussed here and corresponding methods for implementing redundant devices in a process control network are known, for example, from US Pat DE 691 24 899 T2 . EP 1 006 423 A1 and WO 98/49621 A1 known.

Large scale processes, such as chemical processes, petroleum processing, and other manufacturing and refining processes, include numerous plant facilities located at various locations to measure and control process parameters to thereby perform process control. These plant devices may be, for example, sensors, such as temperature, pressure and flow rate sensors, as well as controls, such as valves and switches.

In the past, in the field of process control, manual operations such as manual reading of level and pressure gauges, turning of valve wheels, etc. have been used to operate the equipment for measurement and control in one process. At the beginning of the 20th century, the use of local pneumatic control began in the field of process control, placing local pneumatic controllers, transfer devices and valve positioners at various locations within a process plant to effect control of particular plant locations. With the emergence of the microprocessor-based distributed control system (DCS) in the 1970's, distributed electronic process control in the field of process control has become prevalent.

As is well known, DCS includes an analog or a digital computer, such as a programmable logic controller, which interfaces with numerous electronic monitoring and control devices, such as electronic sensors, electronic transmitters, current-pressure transducers, valve positioners, etc., in one process are arranged. The DCS computer stores and implements a centralized and often complicated control scheme to effect measurement and control of equipment within the process, thereby controlling process parameters according to a general control scheme. However, the control plan implemented by a DCS is often proprietary to the manufacturer of the DCS controller, which in turn makes it difficult and expensive to upgrade, update, reprogram, and maintain DCS as the DCS vendor executes each of them Activities must be intensively involved. Further, the equipment that may be used in or connected to a particular DCS may, due to the proprietary nature of the DCS controller and the fact that a supplier of a DCS controller, have certain facilities or functions of equipment other than those of others Vendors may not be supported, may be restricted.

To solve some of the problems associated with the use of proprietary DCSs, the process control industry has developed a number of standard, open communication protocols including, for example, the HART ^® -, PROFIBUS ^® - WORLDFIP ^® - LONWORKS ^® - Device-Net , and CAN protocol, which allow plant equipment manufactured by different manufacturers to be used together within the same process control network. In fact, any equipment that matches one of these protocols can be used within a process to communicate with and be controlled by a DCS controller or other controller supporting that protocol, even if that equipment is from another Manufacturer was manufactured as the manufacturer of the DCS control device.

In addition, there is a current tendency within the process control industry to decentralize process control and thereby simplify DCS controllers or eliminate the need for DCS controllers to a high degree. Decentralized control is accomplished by having process controllers, such as valve positioners, transmitters, etc., execute one or more process control functions and then communicating data over a bus structure for use by other process controllers in the execution of other control functions. To implement these control functions, each process controller includes a microprocessor capable of performing one or more control functions as well as communicating with other process controllers using a standard open communication protocol. In this way, plant equipment manufactured by different manufacturers can be interconnected within a process control network so that they communicate with each other and one or more Performing process control functions by forming a control loop without the intervention of a DCS control device. The all-digital two-wire bus protocol, now marketed by the Fieldbus Foundation and known as the FOUNDATION ^™ Fieldbus Protocol (hereafter referred to as the "fieldbus"), is an open communication protocol that allows devices manufactured by different manufacturers to operate over one Standard bus work together and communicate to effect a decentralized control in one process.

The bus includes various sections or segments that are separated by bridge devices, such as controllers. Each segment connects a subset of devices connected to the bus to facilitate communication between the devices to control the process. The controllers communicate with the devices in the segments via input / output devices (I / O). The I / O devices implement the communication protocol used in the process control network and control the communication between the controllers and the devices in the segments. Although the I / O devices facilitate communication between the controllers and the devices in the segments, if the I / O device for that segment becomes inoperative for any reason, process control is interrupted, at least with respect to the devices in a particular segment.

The effects of a disabled I / O device and the interruption of process control can be reduced by providing a backup I / O device which is connected to the segment and which takes over the function of the inoperative I / O device. However, the transition from the inoperable I / O device to the standby I / O device is not seamless and interruption of process control still occurs. Currently known spare I / O devices are not updated with the current information stored in the main I / O device, such as current values of process variables, functional software stored in the I / O device may be, the communication plans for the devices in the segment, and the like. Also, in some implementations, the backup I / O device does not automatically take over control when the main I / O device becomes inoperative, delaying execution of the process control until a user releases the backup I / O device. Device activated. In addition, in some communication protocols, such as the fieldbus protocol, the devices are configured to communicate specifically with the main I / O device and must be reconfigured to work with the backup I / O device. Device communicate before the reserve I / O device can take over the communication for these segments. Therefore, there is a need for a redundant bus I / O device in process control networks that seamlessly and transparently handles the functions of a malfunctioning main I / O device without interrupting the implementation of process control in the process control network.

The above object is achieved by the process control system according to claim 1, the method according to claim 16 and the redundant device pair according to claim 31.

The present invention is directed to a method and apparatus for implementing redundant devices in a process control network, such as a distributed control functions network. The method and apparatus of the present invention utilize a pair of redundant devices, such as redundant I / O devices, that are communicatively coupled to a segment of the bus in parallel with each other and in series between the controller and equipment in the segment. The redundant devices are assigned a publish virtual address, which may be the unique address of one of the redundant devices used in communication over the bus. At any one time, one of the redundant devices operates in an active mode and communicates with the devices in the process control network, and the other redundant device operates in a backup mode in which the redundant device maintains a communication link with the devices and listens for communications from the devices but are not responsive to messages from other devices until the device switches to the active mode. Both redundant devices transmit messages over the bus using the virtual publication address so that their messages are identical and are received and processed by the equipment, regardless of which redundant device is active. The redundant devices are configured to detect when the active device is inoperative or about to become inoperative, and the backup device automatically switches to active mode and communicates with the controller and the equipment.

By using the virtual publication address in their communication, the redundant devices become the others Consider facilities as a single virtual device that is in continuous communication, even if one of the physical devices is taken out of service for any reason. Since both redundant devices transmit messages using the virtual publication address, the equipment need not be reprogrammed to receive messages with the address of the redundant backup device when the backup device becomes the active redundant device, thus reducing or eliminating the interruption of process control and communication is eliminated when the active redundant device becomes inoperative.

According to one aspect of the present invention, each device including the redundant devices has a publishing buffer for storing messages to be transmitted over the bus and a subscriber buffer for storing messages received from other devices. The backup mode redundant device receives in its subscriber buffer messages published by other devices intended for the virtual device. In addition, the redundant backup device receives messages transmitted from the active redundant device over the bus and stores those messages in its release buffer. By processing and storing the messages in this manner, the redundant backup device has the current information required to become active as an active redundant device immediately without user intervention or system reprogramming the redundant backup device with current information.

In accordance with another aspect of the present invention, the redundant devices detect that they are part of a redundant pair based on their physical connections to the bus and each other. In an alternative embodiment, the redundant devices are communicatively coupled to each other via a direct communication link that extends outside the bus. The redundant devices may exchange status information, process data, alarm messages, and the like over the communication link. Alternatively, the redundant devices may be configured to sense the connection port or slot or configuration of the connection port or slot to which the redundant devices are located, thereby determining that they are part of a pair of redundant devices and that they either the active redundant device or the redundant backup device are. With this configuration, inoperative redundant devices may be replaced, the redundant substitute becoming operational as part of the virtual device without the need to reconfigure the redundant device so that it can operate as part of the redundant device pair.

According to another aspect of the present invention, the other devices in the system, such as a host device that includes a user interface and a graphics display, may be configured to control the configuration of the connection ports or slots for the redundant devices and the connections of facilities to these. Upon detection, the host device may format the graphics display with information representing the presence of the redundant devices, the operating mode of each of the redundant devices, the operating status of the redundant devices, and the like.

The features and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description of the preferred embodiments with reference to the accompanying drawings.

1 Fig. 10 is a schematic block diagram of a process control network using the fieldbus protocol;

2 Fig. 10 is a schematic block diagram of a field bus device having three functional blocks;

3 is a schematic block diagram illustrating the functional blocks within some devices of the process control network in FIG 1 represents;

4 is the schematic representation of a control loop as a typical process control loop within the process control network in 1 ;

5 is a timing diagram for a macrocycle of a segment of the bus of the process control network in 1 ;

6 Fig. 10 is a schematic functional block diagram of a process control network including redundant bus I / O devices;

7 is a schematic block diagram of the process control network in 6 ; and

8th is a schematic representation of the backplane for implementing the redundant bus I / O devices in 6 ,

The redundant devices of the present invention will be described in detail in the context of a process control network that implements process control functions in a decentralized or distributed manner using a set of fieldbus devices. It should be noted, however, that the redundant devices of the present invention may be used with process control networks that perform distributed control functions using other types of equipment and communication protocols, including protocols not based on two-wire bus systems, and protocols that use only analog or support both analog and digital communication. For example, the redundant devices of the present invention can be used in a process control network that performs distributed control functions, even if that process control network uses HART or PROFIBUS communication protocols, etc., or any other communication protocols currently in existence or developed in the future. Further, the redundant devices of the present invention may also be used with standard process control networks that do not perform distributed control functions, such as HART grids, etc., and may be used with any desired process control device, including valves, positioning devices, transmission devices, etc.

Before discussing the details of the redundant devices of the present invention, generally the fieldbus protocol, plant devices (also known and / or referred to as field devices or devices) configured in accordance with this protocol, and the manner in which communication occurs in a process control network, which uses the fieldbus protocol described. It should be understood, however, that although the fieldbus protocol is a relatively new fully digital communication protocol developed for use in process control networks, this protocol is well known in the art and is described in numerous articles, brochures, and technical descriptions, inter alia The Fieldbus Foundation, a nonprofit organization headquartered in Austin, Texas, is published, distributed and made available, described in detail. In particular, the fieldbus protocol and the type of communication and data storage with devices using the fieldbus protocol is described in detail in the Fieldbus Foundation manuals titled Communications Technical Specification and User Layer Technical Specification which are hereby expressly incorporated by reference in their entirety.

The fieldbus protocol is a full digital serial two-way communication protocol that provides a standardized physical interface to a two-wire loop or bus that interconnects equipment such as sensors, actuators, controllers, valves, etc. that are used in an instrumentation or process control environment, for example Factory or a plant are arranged. The fieldbus protocol actually provides a local area network for plant equipment within a process plant, which enables those plant facilities to perform control functions at distributed locations over a process and to communicate with each other before and after execution of those control functions to implement an overall control strategy , Because the fieldbus protocol allows control functions to be distributed across an entire process control network, it reduces or eliminates the complexity of a centralized process controller, which typically belongs to a DCS.

As 1 can show a process control network 10 using the fieldbus protocol, a host 12 included with a number of other devices, such as a program logic controller (PLC). 13 , a number of control devices 14 , another host device 15 and a group of facility facilities 16 . 18 . 20 . 22 . 24 . 26 . 28 . 30 and 32 via a two-wire fieldbus loop or a bus 34 connected is. The network 10 may also include other facilities, such as a bus monitor 35 who is the bus 34 constantly monitors and collects communication and diagnostic information used to evaluate the performance of the network. The bus 34 contains different sections or segments 34a . 34b and 34c passing through bridge facilities 30 and 32 are separated, which may be control units. Each of the sections 34a . 34b and 34c connects a subset of facilities to the bus 34 are connected to allow communication between the devices in the manner described below. Of course, the network of 1 for illustrative purposes only, and there are many other ways a process control network can be configured using the fieldbus protocol. Typically, in one of the facilities, such as the hurry 12 , a configuration device that is responsible for setting up or configuring each of the devices (which are "smart" devices in that they each include a microprocessor capable of performing communication functions and, in some cases, control functions ), as well as to recognize when new plant equipment to the bus 34 be connected when plant equipment from the bus 34 to be removed some of the facilities 16 to 32 captured data and to interface with one or more user terminals located in the host 12 can be arranged or in any other with the host 12 may be arranged in any manner connected device.

The bus 34 supports or allows purely digital two-way communication and may also provide a power signal to or to all devices connected to it, such as the equipment 16 to 32 , Alternatively, all or some of the facilities 12 to 32 have their own power supply or may be connected to an external power supply via separate lines (not shown). While in 1 the facilities 12 to 32 are shown as being with the bus 34 are connected in a standard bus connection in which a plurality of devices are connected to the same pair of lines that the bus segments 34a . 34b and 34c The Fieldbus protocol allows other device / wiring topologies, including point-to-point connections, in which each device is connected to a controller or host via a separate two-wire pair (similar to a typical 4-20 mA analog DCS system) and a tree or "stab" connection, where each device is provided with a common point in a two-wire bus, which may be, for example, a switch box or a docking area in one of the plant devices within a process control network.

According to the fieldbus protocol, data about the different bus segments 34a . 34b and 34c with the same or different communication baud rates or speeds. For example, the fieldbus protocol provides a 31.25 Kbps communication speed (H1), which is represented by the bus segments 34b and 34c in 1 and higher communication speeds (H2) typically used for advanced process control, remote I / O, and high-speed automation applications, and in the representation of the bus segment 34a in 1 is used. Accordingly, data about the bus segments 34a . 34b and 34c according to the fieldbus protocol using signaling in voltage mode or in current mode. Of course, the maximum length of the segments of the bus 34 not strictly limited, but is determined by the communication speed, cable type, wire size, bus performance option etc. of this section.

The fieldbus protocol shares the facilities with the bus 34 can be connected in three categories, namely base facilities, link masters and bridge facilities. Basic facilities (such as the facilities 18 . 20 . 24 and 28 in 1 ) can communicate, that is communication signals in the bus 34 however, they are not able to control the sequence or timing of communication on the bus 34 expires. Link master devices (such as the facilities 16 . 22 and 26 as well as the host 12 in 1 ) are facilities that are over the bus 34 communicate and are able to control the flow and timing of the communication signals on the bus 34 to control. Bridge equipment (such as the facilities 30 and 32 in 1 ) are devices that are configured to communicate over and connect individual segments or branches of a fieldbus bus to form larger process control networks. If desired, bridge devices may perform a conversion between different data rates and / or different data signaling formats that are present on the different segments of the bus 34 can be used between the segments of the bus 34 amplify ongoing signals that can be between the various segments of the bus 34 filter floating signals and pass only those signals destined for reception by a device in one of the bus segments to which the bridge is connected, and / or can perform other actions for connecting different segments of the bus 34 required are. Bridge devices connecting bus segments operating at different speeds must have link master capabilities on the side of the low speed segment of the bridge. The hosts 12 and 15 , the PLC 13 and the controllers 14 may be any type of fieldbus device, but are typically link master devices.

Each of the facilities 12 to 32 is able to over the bus 34 and may be capable of independently performing one or more process control functions using data received from the device, from the process or from another device via communication signals on the bus 34 to be carried out. Fieldbus devices are therefore able to directly implement portions of an overall control strategy, which in the past has been performed by a centralized digital controller of a DCS. To perform control functions, each fieldbus device includes one or more standardized "blocks" implemented in a microprocessor within the device. In particular, each fieldbus device includes one Resource block and may contain zero or more function blocks and zero or more transducer blocks. These blocks are called block objects.

A resource block stores and communicates device-specific data associated with some of the features of a fieldbus device, including, for example, the device type, the device revision indication, and indications of where other device-specific information can be obtained within a memory of the device. While different device manufacturers can store different types of data in the asset block of a facility, each facility corresponding to the fieldbus protocol contains a resource block that stores some data.

A function block defines and implements an input function, an output function, or a control function associated with the equipment, and thus function blocks are generally referred to as input / output and control function blocks. However, other categories of function blocks, such as hybrid function blocks, may be present or developed in the future. Each input or output function block generates at least one process control input (such as a process variable from a process measuring device) or a process control output (such as a valve position sent to an actuator), while each control function block uses an algorithm (which may be proprietary). to generate one or more process outputs from one or more process inputs and control inputs. Examples of standard function blocks include Analog Input (AI), Analog Output (AO), Bias (B), Control Selection (CS), Discrete Input (DI), Discrete Output (DO), Manual Load (ML), Proportional / Derivative / PD), Proportional / Integral / Derivative (PID), Ratio (RA) and Signal Selection (SS). However, other types of function blocks are present and new types of function blocks can be determined or created to operate in the fieldbus environment.

A transducer block connects the inputs and outputs of a functional block to local hardware devices, such as sensors and actuators, to allow function blocks to read the outputs from local sensors and instruct local devices to perform one or more functions, such as a valve element move. Transducer blocks typically contain information necessary to interpret signals supplied by a local device and to properly control local hardware devices, including, for example, information indicating the nature of the local device, calibration information associated with a local device, etc. single transducer block is typically associated with each input or output function block.

Most functional blocks are capable of generating alarm or event indications based on predetermined criteria and are capable of operating differently in different modes. Generally speaking, function blocks may operate in an automatic mode in which, for example, the algorithm of a function block operates automatically; in an operator mode in which the input or output of, for example, a function block is manually controlled; in an inoperability mode where the block is not working; in a cascade mode, in which the operation of the block is affected (or determined) by the output of another block; and in one or more remote control modes in which a remote computer determines the mode of the block. Other modes of operation, however, exist in the fieldbus protocol.

It is important that each block is capable of communicating with other blocks in the same or different plant devices via the field bus bus 34 communicate using standard message formats defined by the fieldbus protocol. As a result, combinations of functional blocks (in the same or different devices) can communicate with each other to form one or more decentralized control loops. For example, a PID function block in a facility may be over the bus 34 be so connected as to receive an output of an AI function block in a second facility to output data to an AO function block in a third facility and receive an output of an AO function block as feedback to a process control circuit separate from and adjacent to one Form DCS controller. In this way, combinations of function blocks relocate control functions from a centralized DCS environment, allowing multifunction DCS controllers to perform monitoring or coordination functions, or render them completely redundant. Furthermore, function blocks provide a graphical, block-oriented structure for easy configuration of a process and allow the distribution of functions among equipment from different suppliers as these blocks use a consistent communication protocol.

While the block objects discussed here in the context of the fieldbus protocol as "function blocks" It will be apparent to one of ordinary skill in the art that process control networks that use other communication protocols include process function modules that are analogous to the functional blocks described. Thus, while the examples in the following disclosure focus on the fieldbus protocol, the present invention is useful in networks that use other communication protocols and is not limited to process control networks using the fieldbus protocol.

In addition to containing and implementing block objects, each facility includes one or more other objects, including connection objects, trend objects, alarm objects, and view objects. Connection objects define the connections between the input and output of blocks (such as function blocks) both internally in the plant equipment and over the fieldbus bus 34 ,

Trend objects allow local trend development of function block parameters for access by other devices, such as the host 12 and the controllers off 1 , Trend objects contain short-term historical data, for example, associated with some functional block parameters, and report that data to other devices or functional blocks over the bus 34 in an asynchronous way. Alarm objects report alarm conditions or events over the bus 34 , These alarm conditions or events may relate to any event occurring within a device or one of the blocks of devices. Viewing objects are predefined groupings of block parameters used in a standardized human-machine interface, and may from time to time be sent to other means for viewing.

In 2 is now a fieldbus device, which is for example one of the plant facilities 16 to 28 out 1 can act, presented. It contains three resource blocks 48 , three functional blocks 50 . 51 and 52 , and two transducer blocks 53 and 54 , One of the function blocks (which may be an input function block) is above the transducer block 53 with a sensor 55 connected, which may be, for example, a temperature sensor, a setpoint input sensor, etc. The second function block 51 (which may be an output function block) is above the transducer block 54 with an output device, such as a valve 65 , connected. The third function block 52 (which can be a control function block) has a trend object 57 associated with it to trend development of the input parameter of the function block 52 perform.

connection objects 58 define the block parameters of each of the associated blocks and alarm objects 59 send alarm or event messages for each of the associated blocks. View objects 60 are each of the functional blocks 50 . 51 and 52 are assigned and contain or group data lists for the function blocks to which they are assigned. These lists contain information that is required for each group of different defined views. Of course serves 2 by way of example only and other numbers and types of block objects, connection objects, alarm objects, trend objects, and viewing objects may be provided in each facility.

In 3 shows a block diagram of the process control network 10 in which the facilities 16 . 18 and 24 are shown as positioning / valve devices and the facilities 20 . 22 . 26 and 28 as transmission devices, further the functional blocks, the positioning / valve device 16 , the transmission device 20 and the bridge 30 assigned. As 3 shows contains the positioning / valve device 16 a resource block 61 (RSC), a transducer block 62 (XDR) and a number of function blocks, including an analog output function block 63 (AO), two PID function blocks 64 and 65 and a signal selection function block 69 (SS). The transmission device 20 contains a resource block 61 , two transducer blocks 62 and two analog input function blocks 66 and 67 (AI). Further, the bridge contains 30 a resource block 61 and a PID function block 68 ,

As you can see, the different functional blocks in 3 in a number of control loops (by communication over the bus 34 ) and the control circuits, in which the functional blocks of the positioning / valve device 16 , the transmission device 20 and the bridge 30 are arranged in 3 by a loop identification block associated with each of these functional blocks. As in 3 are shown as the AO function block 63 and the PID function block 64 the positioning / valve device 16 and the AI function block 66 the transmission device 20 connected within a loop called CIRCLE1, while the SS function block 69 the positioning / valve device 16 , the AI function block 67 the transmission device 20 and the PID function block 68 the bridge 30 are connected together in a loop, which is referred to as KREIS2. The other PID function block 65 the positioning / valve device 16 is connected within a loop called CIRCLE3.

The interlinked function blocks, which correspond to the one with CIRCLE1 in 3 are designated in detail in the schematic representation of this control loop in 4 shown. How out 4 can be seen, the loop KREIS1 completely by communication links between the AO function block 63 and the PID function block 64 the positioning / valve device 16 and the AI function block 66 the transmission device 20 ( 3 ) educated. The representation of the control loop in 4 shows the communication links between these function blocks using lines that link the process and control inputs and outputs of these function blocks. The output of the AI function block 66 which may include a process measurement or process parameter signal is over the bus segment 34b with the input of the PID function block 64 in communication connection having an output containing a control signal in communication with an input of the AO function block. An output of the AO function block 63 containing a feedback signal, for example, the position of the valve 16 is with the control input of the PID function block 64 connected. The PID function block 64 uses this feedback signal along with the process measurement signal from the AI function block 66 to properly control the AO function block 63 implement. Of course, those in the control loop diagram of 4 lines represented internally within a plant device when the functional blocks are within the same plant device as in the AO and PID functional blocks 63 and 64 the case is (for example, the positioning / valve device 16 ), or these connections can be made over the two-wire communication bus 34 be implemented using standard synchronous fieldbus communication. Of course, other control loops are implemented by other functional blocks that communicate in other configurations.

To implement and execute the communication and control activities, the fieldbus protocol uses three generic technology categories called a physical layer, a communication "stack", and a user layer. The user layer contains the control and configuration functions provided in the form of blocks (such as function blocks) and objects in a particular process controller or equipment. The user layer is typically designed in a proprietary manner by the device manufacturer, but must be able to receive and send messages in accordance with the standard message format defined by the fieldbus protocol and be configured by a user in a standardized manner. The physical layer and the communications stack are required to facilitate communication between different blocks of the various equipment in a standardized manner using the two-wire bus 34 and can be modeled by the well-known Open Systems Interconnect Layer Communication Model (OSI).

The physical layer, that of the OSI layer 1 is in every facility and the bus 34 embedded and operates so that they from the fieldbus transmission medium (the two-wire bus 34 ) converts received electromagnetic signals into messages that can be used by the communication "stack" of the equipment. The physical layer can mentally be considered the bus 34 and those on the bus 34 be presented at the inputs and outputs of the system device existing electromagnetic signals.

The communication stack present in each fieldbus device contains a data link layer, that of the OSI layer 2 corresponds to a fieldbus access sublayer and a fieldbus message specification layer, that of the OSI layer 7 equivalent. For the OSI layers 3 to 6 There is no corresponding structure in the fieldbus protocol. Each layer in the communication stack is for encoding or decoding a portion of the message or signal that is on the fieldbus bus 34 be responsible. As a result, each layer of the communication stack adds or removes certain portions of the fieldbus signal, such as preamble, start delimiter, and end delimiter, and in some cases decodes the stripped portions of the fieldbus signal to identify where the remainder of the signal or message is should be sent or whether the signal should be removed, for example, because it contains a message or data for functional blocks that are not within the received facility.

The data link / physical layer controls the transmission of messages on the bus 34 and manages access to the bus 34 according to a deterministic centralized bus scheduler called active call scheduler and described in detail below. The data link / physical layer removes a preamble from the signals on the transmission medium and can use the received preamble to synchronize the system device's internal clock signal with the incoming field bus signal. Accordingly, the data link / physical layer converts messages in the communication stack into physical fieldbus signals and encodes these signals with clock information to produce a "synchronous serial" signal which provides a proper preamble for transmission on the two-wire bus 34 Has. During the decoding process, the data link / physical layer recognizes special codes within the preamble, such as start delimiters and end delimiters, to identify the beginning and end of a particular fieldbus message, and may execute a checksum to check the integrity of the signal or message, the one from the bus 34 is received, verify. Accordingly, the data link / physical layer transmits fieldbus signals to the bus 34 by adding start and end delimiters to messages in the communication stack and placing those signals on the transmission medium at the proper time.

The fieldbus message specification layer allows the user layer (ie, the functional blocks, objects, etc. of a plant device) via the bus 34 communicate using a standard set of message formats and describes the communication services, message formats and protocol behavior required to set up messages to be placed on the communication stack and to be made available to the user layer. Since the fieldbus message specification layer provides standardized user layer communication, specific fieldbus message specification communication services are defined for each type of objects described above. For example, the fieldbus message specification layer includes an object dictionary service that allows a user to read an object dictionary of a device. The object dictionary stores object descriptions that describe or identify each of the objects of a device (such as block objects). The fieldbus message specifying layer further includes a context management service that allows a user to read and modify communication relationships known as virtual communication relationships (VCRs), described below, associated with one or more objects of a device. Further, the fieldbus message specification layer provides a variable access service, event service, upload and download service, and a program polling service, which are known in the fieldbus protocol and therefore will not be discussed in detail here. The field bus access sublayer maps the fieldbus message specification layer into the data link layer.

To facilitate or allow the operation of these layers, each fieldbus device includes a management information base (MIB), which is a database containing VCRs, dynamic variables, statistics, active link scheduler schedules, functional block execution schedules, and device identifier and scheduling schedules Stores address information. Of course, the information within the MIB can be accessed at any time using standard fieldbus messages or commands, and these can be changed. Further, a device description is usually provided in each device to give a user or host a detailed overview of the information in the VFD. A device description, which typically must be tokens to be used by a host, stores information required by the host to understand the meaning of the data in a device's VFDs.

It should be understood that to implement a control strategy using function blocks distributed across a process control network, the execution of the function blocks must be accurately scheduled in relation to the execution of other function blocks in a particular control loop. Accordingly, the communication between different function blocks on the bus needs 34 be scheduled exactly so that the proper data is made available to each function block before that block starts to execute.

Hereinafter, referring to 1 describes the manner in which various plant devices (and various blocks within the plant equipment) communicate over the fieldbus transmission medium. For communication to proceed, a link master device operates in each segment of the bus 34 (For example, the facilities 12 . 16 and 26 ) as an Active Link Scheduler (LAS) that actively communicates in the associated segment of the bus 34 plans and controls. The LAS for each segment of the bus 34 stores and updates a communication plan (an active connection plan) containing the times that each function block of each device is scheduled to allocate to the periodic communication activity over the bus 34 and the length of time this communication activity should occur. While only one active LAS device in each segment of the bus 34 may be present, other link master devices (such as the device 22 in the segment 34b ) serve as reserve LAS and become active if, for example, the current LAS fails. Base facilities do not have the ability to take on the role of LAS at any time.

Generally speaking, communication activities are over the bus 34 in repetitive Macrocycles are classified, each of which provides a synchronous communication flow for each function block publishing over the bus, on a respective segment of the bus 34 is active, and one or more asynchronous communication flows for one or more of the functional blocks or devices operating on a segment of the bus 34 are active contains. A device may be active, that is, data to any segment of the bus 34 send and receive data from this, even if they are physically connected to another segment of the bus 34 is connected, through coordinated operation of the bridges and the LAS on the bus 34 ,

During each macrocycle, each of the functional blocks executes on a particular segment of the bus 34 are active, usually at different but exactly assigned (synchronous) times, execution and at another precisely assigned time publish its output data to the segment of the bus 34 in response to a forced data command generated by the corresponding LAS. Preferably, each functional block is scheduled to be scheduled to publish its output data shortly after the end of the execution period of the functional block. Furthermore, the data publishing times of the various function blocks in series are scheduled so that there are not two function blocks in a particular segment of the bus 34 publish data simultaneously. In turn, during the time during which there is no synchronous communication, each facility is allowed to transmit alarm data, viewing data, etc. in an asynchronous manner using token controlled communication. As noted above, the times are for sending the forced data instructions to each of the devices on a segment of the bus 34 stored in the MIB of the LAS device for that segment. These times are typically stored as offset times since they identify the times at which a function block is to execute or send data as a relative reference to the beginning of an "absolute connection schedule start time", all with the bus 34 associated facilities is known.

To accomplish communication during each macrocycle, the LAS sends, for example, the LAS 16 of the bus segment 34b , a forced data command to each of the devices on the bus segment 34b according to the list of transmission times stored in the active connection plan. Upon receipt of a forced data command, a function block of a device publishes its output data to the bus 34 for a certain period of time. Since each of the functional blocks is typically designed to execute the execution of this block just before the block is to receive a forced data command, the data published in response to a forced data command should be the most recent output of the functional block. However, if a function block is slow to execute and has not stored new output signals when it receives the compulsory data command, the function block publishes the output data generated during the last execution of the function block and indicates that the published data is old data.

After the LAS issues a forced data command to each of the function blocks on a particular segment of the bus 34 and during the time the function blocks are executed, the LAS may cause the occurrence of asynchronous communication activities. To effect asynchronous communication, the LAS sends a pass token message to a particular facility. When a facility receives a pass token message, that facility has full access to the bus 34 (or a segment thereof) and may send asynchronous messages, such as alarm messages, trend data, operator setpoint data, etc., until the messages are completed or until a maximum assigned "token hold time" has elapsed. Subsequently, the installation device gives the bus 34 (or a particular segment thereof) and the LAS sends a pass token message to another device. This process is repeated until the end of the macrocycle or until the LAS schedules a forced data command to effect a synchronous communication. Of course, depending on the extent of message traffic and the number of devices and blocks that are associated with a particular segment of the bus 34 Not every device receives a pass token message during each macrocycle.

5 shows a timing diagram illustrating the times during which the function blocks on the bus segment 34b in 1 during each macrocycle of the bus segment 34b are executed, and the times during which synchronous communication during each macrocycle, the bus segment 34b is associated with occurs. In the timing diagram of 5 the time is indicated on the horizontal axis and the various function blocks of the positioning valve device 16 and the transmission device 20 (in 3 ) are plotted on the vertical axis. The control loop in which each of the function blocks works is in 5 indicated as index. So AI _KREIS1 refers to the AI function _block 66 the transmission device 20 , PID _CIRCLE1 refers to the PID function _block 64 the positioning / valve device 16 etc. The Block execution time of each of the illustrated functional blocks is represented by a hatched field, while each scheduled synchronous communication is represented by a vertical bar in FIG 5 is marked.

Thus, according to the timing chart in FIG 5 during a particular macrocycle of the segment 34b ( 1 ), the AI _KREIS1 function _block for the first by the field 70 specified period of time. Subsequently, during the time taken by the vertical bar 72 is indicated, the output signal of the function _block AI _KREIS1 on the bus segment 34b in response to a forced data command from the LAS for the bus segment 34b released. The fields show accordingly 74 . 76 . 78 . 80 and 81 the execution _{times of} the function _blocks PID _CIRCLE1 , AI _CIRCLE2 , AO _CIRCLE1 , SS _CIRCLE2 and PID _CIRCLE3 respectively (which are different for the different blocks, respectively), while the vertical bars 82 . 84 . 86 . 88 and 89 designate the times in which the function _blocks PID _CIRCLE1 , AI _CIRCUIT2 , AO _CIRCLE1 , SS _CIRCLE2 and PID _CIRCLE2 respectively contain data on the bus segment 34b publish.

It is obvious that the timing diagram of 5 also represents the times available for asynchronous communication activities which may occur during the execution times of each of the function blocks and during the time to the end of the macrocycle during which no function blocks are executed and if no synchronous communication on the bus segment 34b expires. Of course, if desired, different functional blocks may be deliberately scheduled in time to be executed at the same time, and not all functional blocks must publish data to the bus, for example, if no other device subscribes to the data generated by a functional block.

Plant facilities are able to communicate with each other via the bus 34 communicate using unique addresses assigned to each facility. The plant facilities are at nodes of the bus 34 and each node has a particular physical address that identifies the plant equipment located thereon for use in communicating with other plant facilities in the process control network. The unique address for the facility is stored in the MIB of the facility and the address is included in the messages published by the facility on the bus. The equipment or devices for which the messages are published are configured with VCRs that direct the device, the bus segment 34 to monitor messages containing the address of the publishing facility. When the participating equipment detects messages with the address of the publishing equipment, they decode and process the messages according to the requirement to perform the process control.

Facilities facilities are able to transfer data and messages over the bus 34 using one of three types of VCRs defined in the fieldbus access sublayer of the stack of each facility. A client / server VCR becomes queued, unplanned, user-initiated, one-to-one communication between the devices on the bus 34 used. Such queued messages are sent and received in the order in which they are entered for transmission according to their priority, without overwriting any previous messages. Thus, a facility may use a client / server VCR when receiving a pass token message from a LAS to send a request message to another facility on the bus 34 to send. The requesting device is called "client" and the device that receives the request is called "server". The server sends a response when it receives a pass token message from the LAS. The client / server VCR is used, for example, to effect operator-initiated requests such as set point changes, tuning parameter access and changes, alarm acknowledgments, and device uploads and downloads.

A report distribution VCR is used for queued, unplanned, user initiated communications from one station to multiple stations. For example, if a facility with an event or trend report receives a pass token from a LAS, that facility sends its message to a "group address" defined in the fieldbus access sublayer of the communication stack of that facility. Devices configured to monitor this VCR receive the report. The report distribution VCR type is typically used by fieldbus devices to send alarm messages to operator consoles.

A Publication Subscriber VCR type is used for buffered communications from one station to multiple. Buffered communications are those that store and transmit only the latest version of the data so that new data completely overwrites previous data. Function block issues contain, for example, buffered data. A "publishing" facility will publish or send a message using the Publication / Participant VCR Type to all "participating" facilities on the bus 34 when the publishing entity receives a compulsory data message from the LAS or from a participating institution. The publish / subscribe relationships are predetermined and defined and stored within the fieldbus access sublayer of the communication stack of each facility.

To communicate properly on the bus 34 Each LAS periodically sends a time distribution message to all plant devices that are connected to a segment of the bus 34 which enables the receiving devices to synchronize their local application time with each other. Between these synchronization messages, the clock time is independently maintained in each device based on its own internal clock. The clock synchronization allows the system equipment to provide data on the entire field bus network with time stamps, and for example to indicate when data was generated.

Further, each LAS (and every other link master device) stores in each bus segment a "live list" which is a list of all devices associated with that segment of the bus 34 that is, all devices that respond properly to a pass token message. The LAS continually recognizes new devices that are added to a bus segment by periodically sending probe node messages to addresses that are not on the live list. In fact, each LAS must check at least one address with the probe after completing a transmit cycle of pass token messages to all plant devices in the live list. If a facility is present at the tested address and receives the probe node message, the facility immediately returns a probe response message. Upon receiving a probe-response message, the LAS adds the setup to the live list and confirms this by sending a node activation message to the tested facility. An attachment remains on the live list as long as that attachment properly responds to pass token messages. However, a LAS removes an attachment from the live list if the attachment either does not use the token after three consecutive attempts or does not send the token directly back to the LAS. When an attachment is removed from or added to the live list, the LAS sends changes to the live list to all other link masters in the corresponding segment of the bus 34 to ensure that each link master device maintains an up-to-date copy of the live list.

As 1 and as discussed above, the bridge means 30 and 32 Control devices that implement process control schemes or routines that contain a number of different loops or segments, respectively. Generally speaking, each control loop controls one or more plant devices to control a portion of a process. In order to effect process controls and exchange other information regarding the operation and status of the controlled process, the controllers and the equipment in one segment of the bus transfer messages in the segment. The communication between the controllers and the equipment is facilitated by I / O devices connected to the segment between the controller and the equipment. The MIB of an I / O device is programmed with VCRs which indicate that the I / O device should receive the messages from the controller and the devices and should forward the message along the segment to the appropriate controller or device (s) , Additionally, the I / O device may act as the LAS for the segment and transmit messages on the bus that schedule the control communication in the segment. In addition, the I / O device may include function blocks that perform process control functions. In the context of these latter features, the I / O device itself can transmit messages to the bus address to participating plant devices which detect and decode the messages and process the information contained therein.

Since the I / O device on a segment connects the controller to the equipment, failure of the I / O device interrupts both communication in the segment and execution of the process control until the I / O device is repaired or replaced , An alternative to minimizing the interruption of process control is the incorporation of a spare I / O device in the segment which is activated when the main I / O device becomes inoperable. The pre-installed spare I / O device reduces the interruption by eliminating the need to either repair the I / O device or remove the inoperative I / O device and replace it with a new I / O device to replace. Although the interruption is reduced, the process control is still for a certain period of time due to certain factors that are due to the process control network. For example, the failure of the I / O device must be detected and the user notified so that the backup I / O device can be activated. Additionally, after enabling, the spare I / O device must be reprogrammed with the current data from the disabled I / O device, such as process variables, VCRs, active link schema, if the I / O device is a LAS, and like. In addition, the backup I / O device is assigned its own unique address on the bus and therefore the controller and equipment must be reprogrammed so that they monitor the bus for messages indicating the address of the backup I / O device. Device instead of the address of the main I / O device included. All of these activities require time during which the normal operation of the control loops is interrupted. For these reasons, there is a need for redundant bus I / O devices in which the spare I / O device is constantly updated with the data currently stored in the active I / O device, the spare I / O device automatically becomes the active I / O device when the main I / O device becomes inoperative and the transition from the primary I / O device to the backup controller I / O device and the equipment connected to the segment of the bus is transparent.

In 6 is a process control network 100 in which redundant bus I / O devices could be implemented. The process control network 100 which may be, for example, a DeltaV process control system sold by Fisher Rosemount Systems, Inc. of Austin, Texas, includes one or more controllers 102 , one or more host or operating workstations 104 and / or other computing devices, such as other workstations, databases, configuration stations, etc., that are connected to a bus 110 connected, which may be, for example, an Ethernet bus. It is known that the control device or the control devices 102 and workstations 104 Contain processors that implement software stored in the memories of these devices. The control device 102 For example, it may be a distributed control system controller or any other type of controller implemented, for example, in a personal computer or other device that allows a user or operator to interface with the process control system 100 to form in a known manner.

Numerous installation facilities 112 to 115 are as shown via redundant I / O devices 120 and 122 with the control device 102 which will be described in detail below. The facilities 112 to 115 are with a bus segment 124 connected, which may be any desired bus type, such as a fieldbus connection. In this case, the facilities can 112 to 115 Use the Foundation Fieldbus Communication Protocol. Of course, any of the plant facilities 112 to 115 correspond to any type of plant equipment used in the process control network 100 including, for example, sensors, control valves, positioning devices, blowers, video cameras, microphones, etc. Of course, other devices may connect to the network in any desired manner 100 get connected.

As 6 shows are the redundant I / O devices 120 and 122 in the segment 124 between the controller 102 and the facilities 112 to 115 connected in parallel. For the discussion below, the I / O device becomes 120 as the main I / O device 120 referred to, and the I / O device 122 is called a secondary I / O device 122 designated. As discussed above, each of the I / O devices has 120 and 122 a unique address based on the node to which the device is connected. The control device 102 and the facilities 112 to 115 identify messages from the I / O devices 120 and 122 based on the presence of the address in the on the bus segment 124 transmitted messages. To implement the redundancy, the I / O devices are 120 and 122 configured to act as a single virtual I / O device 130 work with the controller 102 and the facilities 112 to 115 in the same way regardless of which of the I / O devices 120 and 122 in the bus segment 124 is active and communicates. The I / O facilities 120 and 122 Regardless of which device currently the active I / O device of the virtual I / O device 130 is, communicate transparently with the controller 102 , the installation facilities 112 to 115 and the other facilities of the network 100 by publishing messages that have the same address (a virtual publication address). Publishing messages using the virtual publication address will display all the messages from the virtual I / O device 130 are the same and are in the same way by the controller 102 and the facilities 112 to 115 regardless of which I / O device 120 respectively 122 the message actually published.

The virtual publishing address for the virtual I / O device 130 can the unique physical address of one of the I / O devices 120 or 122 or any other unique address, that of the virtual I / O device 130 is assigned. Regardless of the value of the publishing virtual address or the way in which the publish virtual address is assigned, the publish virtual address and the virtual I / O device implementation code become 130 in the communication stack of the I / O devices 120 and 122 saved. In addition, the publishing VCRs in the controller become 102 and the facilities 112 to 115 with the virtual publication address for the virtual I / O device 130 instead of the address of one of the two I / O devices 120 or 122 configured.

During normal operation of the process control network 100 sends and receives one of the I / O devices 120 and 122 active messages on the bus segment 124 , works as the LAS for the bus segment 124 , performs process control functions and the like performed by the virtual I / O device 130 executed to process control in the process control network 100 to effect. In the discussion below, the I / O device is 120 which referred to above as the main I / O device 120 First, the active I / O device for the virtual I / O device 130 , The I / O device not as the active I / O device for the virtual I / O device 130 works, in this case the secondary I / O device 122 , is called the reserve I / O device for the virtual I / O device 130 considered.

While in reserve mode, the spare I / O facility performs 122 none of the process control functions or communication functions of the virtual I / O device 130 out. The reserve I / O device 122 However, this is done with the virtual I / O device VCRs 130 configures and monitors the bus segment 124 on communications that are on the bus segment 124 and for the virtual I / O device 130 are determined. The reserve I / O device 122 Receives and decodes the messages and stores information from the messages that are normally received from the active I / O device 120 would be saved. The backup I / O device may even process information and update data stored therein, receive and store updated active link schedules, and perform all other functions required for the backup I / O device 122 the process control functions of the virtual I / O device 130 can take over when the active I / O device 120 becomes inoperative or is decommissioned for other reasons. As a result, although the spare I / O device 122 Publishing messages while in reserve mode interrupts the backup setup 122 maintains a communication link with the functional block application processes for the devices on the bus to verify the integrity of the communication and to eliminate delays in connection setup during the switch to active mode.

In addition to receiving and processing communications from the plant facilities 112 to 115 to the virtual I / O device 130 are transmitted, receive and store the spare I / O device 122 also the messages received from the active I / O facility 120 or other facilities on the bus 110 be published as the active I / O device of the virtual I / O device 130 to act. This functionality is implemented by the communication stacks of the I / O devices 120 and 122 be programmed so that the reserve I / O device 122 Messages monitored by the active I / O device 120 to be published. Any facility over the bus 110 has both a publish buffer for compiling and storing the messages sent by the device on the bus 110 and a subscriber buffer for storing messages from other devices in the process control network 100 be received. For example, the main I / O device has 120 a publishing buffer 132 and a participant buffer 134 and the secondary I / O device 122 has a publishing buffer 136 and a participant buffer 138 , In previously known devices, the publication buffer stores only messages transmitted from the device and does not receive messages transmitted to the device, and the user buffer stores only messages transmitted to the device and no messages sent from the device Device to be transferred. However, in order to implement the redundant I / O devices and have the spare I / O device take over the functions of the active I / O device with minimal or no interruption in process control, the release buffer of the backup device receives and stores I / O device 122 preferably the most recent release from the release buffer of the active I / O device 120 ,

The reserve I / O device 122 is able to from the active I / O device 120 to receive and store published messages by configuring the communication stack of the redundant I / O devices so that the release buffer of the standby I / O device 122 acts as a message buffer for the message coming from the publish buffer of the active X / O device 120 to be published. During reserve mode, the release buffer will carry the spare I / O device 122 not the normal functions of a publish buffer, such as responding to compulsory data requests and call origination messages. At the same time, the standby I / O device monitors the bus segment 124 on published messages, which are the virtual publication address for the virtual I / O device 130 to have. if any of the active I / O device 120 released, decodes the reserve I / O facility 122 the message and saves the message in their publishing buffer instead of their subscriber buffer. If the reserve I / O device 122 assumes the functions of the active I / O device, the release buffer of the new active I / O device has the most recent data from the unavailable I / O device release buffer and is ready to immediately access the function of the inoperative I / O device without the intervention of a user or controller would be required to update the data in the new active I / O device. As soon as the I / O device transitions from the backup mode to the active mode, the I / O device monitors the messages for the virtual I / O device virtual publication address 130 Contain, not further, and pick up the activities of normal status, such as responding to compulsory data commands and connection setup messages.

In addition to connections via the bus segment 124 can the I / O facilities 120 and 122 also a direct communication connection 140 have over which the I / O facilities 120 and 122 communicate with each other in a way that is not necessarily dictated by the communication protocol that is on the bus segment 124 is implemented. The communication connection 140 can any standard connection between the I / O devices 120 and 122 over which the devices can communicate, such as the physical connection between the I / O devices 120 and 122 with the backbone of the bus, a direct hardwired connection between the devices 120 and 122 and the same. The I / O facilities 120 and 122 can exchange any kind of information necessary for the function of the devices as redundant I / O devices and thus for the implementation of the virtual I / O device 130 as described above is required. The information may include communications about which of the I / O devices 120 and 122 is the main I / O device and which is the secondary I / O device, which device is the active device and which is the backup device, and updated information from the active I / O device used for the backup I / O device is required to take over the function as an active I / O device. The I / O devices may also exchange status information indicating that the active I / O device is about to fail or is inoperable. In addition, the I / O facilities can 120 and 122 Have functional blocks used to implement process control and the I / O devices 120 and 122 may exchange information for use by the functional blocks to effect process control.

If the I / O facilities 120 and 122 in the process control network 100 must be installed, the I / O facilities 120 and 122 be aware that they are a pair of redundant I / O devices that one of the I / O devices 120 and 122 the main I / O device is and the other is the secondary I / O device, and that one of the I / O devices 120 and 122 the active I / O device and the other is the reserve I / O device. A method of creating the relationship between the I / O devices 120 and 122 is the exchange of information between the I / O facilities 120 and 122 via the communication link described above 140 , Another way to create the relationship between the I / O devices 120 and 122 is that a user's I / O facilities 120 and 122 programmed directly, or the execution of a programming routine in a host device or an operator workstation 104 that programming the I / O devices 120 and 122 via messages sent over the bus 110 be transmitted. Alternatively, the relationship between the I / O devices 120 and 122 and the other facilities in the process control network 100 be determined by the physical configuration of the devices and / or by the way in which the I / O devices 120 and 122 with the process control network 100 get connected.

In 7 is the physical configuration of the process control network off 6 shown. The control device 102 , the I / O facilities 120 and 122 and other facilities are with the bus segment 124 over a backplane 150 connected, which has a variety of terminals or slots with connectors. The devices are connected to the slots of the backplane and the backplane is configured to properly connect the devices to the bus segment 124 are connected. For example, the process control network 100 out 6 To implement, the backplane is configured so that the slot with which the controller 102 connected in series between the bus 110 and the I / O facilities 120 and 122 is switched, and the slots with which the I / O devices 120 and 122 are connected, in parallel and in series between the control device 102 and the facilities 112 to 115 on the bus segment 124 are switched. While the physical connection of the facilities to the bus 110 mainly for Information exchange between the devices and used to implement the process control, the physical connection can also be used to the I / O devices 120 and 122 and the remaining facilities in the process control network 100 to inform that the I / O facilities 120 and 122 form a redundant pair of I / O devices.

In addition, the connection between the control device 102 and the I / O facilities 120 and 122 used to switch the reserve I / O device 122 to steer into the active mode. For example, the I / O devices 120 and 122 be configured to send status information to the controller 102 transfer. The station information may include alarm messages with the information that the active I / O device 120 becomes inoperable or inoperative in the immediate future. The control device 102 may be programmed to respond to an alarm message by indicating the operating mode of the I / O devices 120 and 122 switches so that the active I / O device 120 the reserve mode and the reserve I / O device 122 takes the active mode. The control device 102 may also be programmed to send a message to a host 104 which indicates that the I / O device 120 must be serviced.

8th shows a schematic representation of the backplane 150 out 7 , The backplane 150 contains a variety of slots 152 to 160 who are each capable of a facility by bus 110 connect to. Each of the slots 152 to 160 has a variety of contact pins 162 which are inserted into associated openings at the associated equipment to provide an electrical connection between the bus 110 and to create the facilities. In addition, the backplane 150 with the appropriate electrical connections between the slots 152 to 160 configured to work with the slots 152 to 160 properly connected to each other, such as the connections for the bus segment described above 124 , In addition, the backplane can 150 and / or I / O facilities 120 and 122 be configured to implement the redundant I / O devices.

An alternative configuration for implementing the redundant I / O devices is certain slots on the backplane 150 for the main I / O device and the secondary I / O device that make up the redundant pair. For example, it may be predetermined that for the process control network 100 the fifth slot 156 and the sixth slot 157 on the backplane 150 for bus segments for redundant I / O devices 120 and 122 are reserved. More specifically, the main I / O device becomes the fifth slot 156 and the secondary I / O device with the sixth slot 157 connected. In this implementation of redundant I / O devices, the I / O devices are 120 and 122 programmed to connect to the fifth or sixth slot 156 or 157 or the designation as either the main I / O device or the secondary I / O device depending on the slot 156 or 157 to which they are connected, as well as the associated standard operating mode, either active or reserve. If one extends the example described above, then the fifth slot 156 the slot position for the main I / O device and the sixth slot 157 can be the slot position for the secondary I / O device. If the I / O facilities 120 and 122 Connected to the backplane becomes the I / O device 120 as the main I / O device with the fifth slot 156 connected and the I / O device 122 , the secondary device, comes with the sixth slot 157 connected. The I / O device 120 detects the connection to the fifth slot 156 and notes that it is the main I / O device of a redundant pair of I / O devices and takes the role of the active I / O device for the virtual I / O device 130 at. Similarly, the I / O device detects 122 the connection with the sixth slot 157 and notes that it is the secondary I / O device of a redundant pair of I / O devices and takes the role of the backup I / O device for the virtual I / O device 130 at. With such a configuration, in the case recognizes that one of the I / O devices 120 and 122 or both become inoperable, a spare I / O device, by virtue of its slot position, is part of a redundant pair, without the need to reprogram the device after connection, which provides additional delay. In addition, the other facilities of the process control network 100 such as the hosts or operator workstations 104 , be programmed to detect the presence of redundant pairs of I / O devices. When capturing I / O devices 120 and 122 , with the fifth or the sixth slot 156 respectively 157 may be the host operating workstations 104 also automatically the displays of the process control network 100 with the redundant I / O devices 120 and 122 To update. Of course, the I / O devices can detect their connection to a particular slot and the redundant operation associated with that slot by configuring pins or other hardware (or software) on the backplane.

Another alternative configuration for implementing the redundant I / O devices without programming the I / O Means required after connection is changing the voltage level of the pins 162 to which the I / O devices are connected. Each of the slots 152 to 160 is with twelve pens 162 to connect the equipment to the slots 152 to 160 the backplane 150 although the use of more or less pens 162 based on the requirements of the bus 110 connected hardware is anticipated. Two contact pins 162 in each slot are required to understand the relationship between the I / O devices 120 and 122 The first pin indicating that the slot is one of a pair of redundant I / O devices and the second pin indicating whether the associated I / O device is the main I / O device or is the secondary I / O device. Just as the I / O devices in the above example were programmed to detect the slot to which they are connected, in this alternative embodiment of the present invention, the I / O devices are programmed to match the voltage level of the designated one Evaluate pins to see if they are part of a redundant pair of I / O devices. In this example, the tenth pins are 164 and 168 of the third and fourth slots 154 respectively 155 is set high to indicate that the I / O devices connected to them are part of a redundant pair of I / O devices. The eleventh pins 166 and 170 the slots 154 respectively 155 are set to a high level to indicate that the slot 154 or 155 the right slot of the redundant pair is low and to a low level to indicate that the slot 154 or 155 is the left slot of the redundant pair. The value of the eleventh pins 166 and 170 Also determines which I / O device is the main device and which is the secondary device. In the present example, a low value is on the eleventh pin 166 or 170 the main I / O device. Consequently, in this example, the two tenth pins 164 and 168 set to high and the eleventh pin 166 of the third slot 154 is set to low to indicate that the slot 154 is the left slot of the pair and that the I / O device connected to it is the main I / O device and the eleventh pin 170 of the fourth slot 155 is set to high to indicate that the slot 155 is the right slot of the pair and that the I / O device connected to it is the secondary I / O device. As in the example described above, the I / O devices become 120 and 122 programmed to evaluate the tenth and eleventh pins of the slots to which they are connected to determine if they are part of a redundant pair of I / O devices and if they are the main I / O device or the secondary I / O device.

In addition, the hosts or operator workstations 104 detect if there is a redundant pair of I / O devices with the bus segment 124 and inform the redundant pair of I / O devices of information to users when such a pair is detected. The hosts or operating workstations 104 may include a user interface having an indication of information regarding the process control network and its facilities. To capture the required process and device data, the host can 104 be configured with an automatic scanning function by which it periodically polls the nodes on the bus to determine if devices are connected and if there are devices to collect information about the device for display to the user. The hurry 104 and / or the equipment may be configured such that the automatic scanning function detects the presence of redundant I / O devices 120 and 122 discovered. For example, the I / O devices 120 and 122 be programmed to transmit messages indicating that the I / O devices 120 are redundant, along with their current mode of operation, and the host 104 can be programmed to receive these messages. Alternatively, the host 104 in a similar way to the I / O facilities 120 and 122 be programmed with information that specified slots for redundant I / O devices 120 and 122 are reserved and detect when a device is connected to the designated slots. Other alternative configurations to the host 104 Recognizing the presence of redundant I / O devices and displaying the information at the user interface are contemplated by the inventors and will be apparent to one of ordinary skill in the art.

While the redundant I / O devices described herein have been implemented in a process control network operating under a fieldbus protocol, it should be appreciated that the redundant I / O functionality described herein may be implemented using other types of programs, hardware, firmware, etc. can be implemented, which belong to other types of control systems and / or communication protocols. While the fieldbus protocol uses the term "function block" to describe a particular type of entity that is capable of performing a process control function, it should be understood that the term function block as used herein is not so limited herein and each Type of device, program, routine or other entity capable of performing a process control function in arbitrary fashion at distributed locations within a process control network. Thus, the redundant I / O devices described and claimed herein may be implemented in process control networks that use other process control communication protocols or schemes (that may or may not currently exist) as long as those networks or protocols allow or provide control functions to distributed ones Places are running within a process. Moreover, while the embodiments disclosed herein are directed to redundant I / O devices, it should be appreciated that the redundant functionality described herein may be implemented using other types of devices for which the implementation of redundancy in the process control network is desired.

Claims (46)

Process control system for communication in a process control network with a plurality of redundant devices of a virtual I / O device ( 130 ), each having a unique address, the process control system comprising: a bus ( 110 ); a redundant main facility ( 120 ) of the virtual I / O device ( 130 ) with a first unique address associated with the bus ( 110 ) is communicatively connected and programmed to publish messages on the bus that have a virtual publication address and a publication buffer ( 132 ) and a participant buffer ( 134 ); a redundant secondary device ( 122 ) of the virtual I / O device ( 130 ) having a second unique address communicatively coupled to the bus and programmed to publish messages on the bus having the virtual publication address and a publication buffer ( 136 ) and a participant buffer ( 138 ); and at least one receiving device communicatively connected to the bus and programmed to process messages published on the bus having the virtual I / O device virtual publishing address; the bus ( 110 ) with the main facility ( 120 ), with the secondary device ( 122 ) and at least one receiving device, and wherein the redundant main device ( 120 ) operates in an active mode in which the redundant main facility ( 120 ) Messages on the bus ( 110 ) for at least one receiving device, and the redundant secondary device ( 122 ) operates in a reserve mode in which the secondary device ( 122 ) does not transmit messages on the bus, and the publication buffer ( 136 ) of secondary equipment ( 122 ) messages received in the reserve mode from the main facility ( 120 ) stores. A process control system according to claim 1, characterized in that the redundant secondary means operates in the active mode when the redundant main means is disabled. A process control system according to claim 1 or 2, characterized in that the redundant secondary means determines that the redundant main device is inoperative when the redundant main device does not transmit messages on the bus containing the virtual publication address. Process control system according to one of the preceding claims, in particular according to claim 2, further comprising a control device connected to the redundant main device ( 120 ) and the redundant secondary device ( 122 ) is communicatively coupled and programmed to receive status information from the main redundant device and the redundant secondary device, and upon receipt of status information indicating that the redundant master device is about to become inoperative or inoperable, causes the redundant master device; to work in reserve mode and the redundant secondary to work in active mode. Process control system according to one of the preceding claims, in particular according to claim 2, characterized in that the redundant main device ( 120 ) and the redundant secondary device ( 122 ) by a communication link ( 140 ) are communicatively coupled to each other outside the bus and the redundant master device is programmed to provide status information indicating that the redundant master is about to become inoperable or inoperable to the redundant secondary device via the communications link (5). 140 ) transmits. Process control system according to claim 1, characterized in that the publication buffer ( 136 ) of the redundant secondary device ( 122 ) in reserve mode via the bus ( 110 ) received messages of the redundant main facility ( 120 ) stores. A process control system according to any one of the preceding claims, in particular claim 1, characterized in that the main redundant device and the redundant secondary device are programmed to process messages having the unique address of at least one device and the redundant main device and the redundant secondary device messages receive and process the unique address of the at least one Have facility while working in the active mode and in the reserve mode. Process control system according to one of the preceding claims, in particular according to claim 1, characterized in that the bus ( 110 ) has a first portion and a second portion, the first and second portions each having at least one device in communication therewith, the redundant main device and the redundant secondary device parallel to each other and in series between the first portion and the second portion of the second portion Buses ( 110 ) are connected in communication connection. Process control system according to one of the preceding claims, in particular according to claim 1, characterized in that the redundant main device ( 120 ) and the redundant secondary device ( 122 ) by a communication link ( 140 ) outside the bus ( 110 ) are communicatively connected with each other. Process control system according to one of the preceding claims, in particular according to claim 1, characterized in that the redundant main device ( 120 ) and the redundant secondary device ( 122 ) are configured to detect the presence of each of the other redundant secondary device and determine which of the redundant main device and the redundant secondary device will operate in the active mode and which will operate in the backup mode. Process control system according to one of the preceding claims, in particular according to claim 1, characterized in that the devices are connected to the bus ( 110 ) are in communication via slots, the system further comprising: a first slot ( 156 ), which is the main redundant facility ( 120 ) by bus ( 110 ) brings into communication connection; and a second slot ( 157 ), the redundant secondary device ( 122 ) by bus ( 110 ) brings into communication connection; wherein the redundant main device and the redundant secondary device are configured to be based on the determination that the redundant main device is connected to the first slot (12). 156 ), determine that the redundant main device is connected to the first slot ( 156 ) and operates in the active mode, and based on the determination that the redundant secondary device (16) 122 ) with the second slot ( 157 ), determine that the redundant secondary device is connected to the second slot ( 157 ) and works in the reserve mode. Process control system of claim 11, characterized in that the first and the second slot each comprise a plurality of contact pins which connect the second redundant means respectively to the first and the second slot, each contact pin having an associated voltage level, the first and whereby the redundant main device and the redundant secondary device determine that the redundant main device with the first slot ( 156 ) and the redundant secondary device with the second slot ( 157 ), based on the voltage levels of the contact pins. A process control system according to any one of the preceding claims, in particular claim 1, further comprising host means having a display in communication with the bus, the host means being configured to detect the presence of the redundant master and the processor detected redundant secondary device detects the operation of the redundant main device in the active mode and the operation of the redundant secondary device in the reserve mode, and on the display of the host device, the presence of the redundant main device and the redundant secondary device, the operation of the redundant main device in the active Mode and the operation of the redundant secondary device in the reserve mode. Process control system according to one of the preceding claims, in particular according to claim 1, characterized in that the virtual publication address is one of the first unique address and the second unique address. Process control system according to one of the preceding claims, in particular according to claim 1, characterized in that the redundant main device and the redundant secondary device are I / O devices. A method of implementing redundant means of a virtual I / O device within a process control system for communicating in a process control network comprising a plurality of devices in communication communication over a bus, each of the redundant devices having and being able to have a unique address is to communicate over the bus, the method comprising: configuring a redundant main device having a first unique address and a redundant secondary device having a second unique address to transmit messages over the bus, which is a virtual publication address , wherein the bus with the main device, with the secondary device and is connected to at least one receiving device; Operating the redundant host in an active mode in which the redundant host transmits messages over the bus having the publish virtual address, the host including a publishing buffer and a subscriber buffer; Operating the redundant secondary in a spare mode in which the redundant secondary does not transmit messages over the bus, the secondary having a publishing buffer and a subscriber buffer; and receiving messages having the virtual publication address at at least one receiving device configured to process messages having the virtual publication address, and storing received messages of the main device in the publishing buffer of the secondary device when the secondary device operates in the spare mode becomes. A method of implementing redundant devices within a process control system in a process control network according to claim 16, further comprising the step of configuring the redundant secondary device to operate in the active mode when the redundant main device is inoperative. A method for implementing redundant devices within a process control system in a process control network according to claim 16 or 17, further comprising the step of configuring the redundant secondary device to transmit based on the fact that the redundant master does not transmit messages on the bus having the virtual publication address, determines that the main redundant device is inoperative. A method of implementing redundant devices within a process control system in a process control network according to any one of claims 16 to 18, further comprising: Transmitting status information on the bus indicating that the redundant master is about to become inoperable or inoperable from the redundant master in a message having the virtual publication address while the redundant master is operating in the active mode; Configuring the redundant secondary device to process the messages having the publish virtual address; and Causing the redundant secondary to operate in the active mode upon receipt of the message containing the publication virtual address and the status information. A method of implementing redundant devices within a process control system in a process control network according to any one of claims 16 to 19, further comprising: Establishing a communication connection of the redundant main device and the redundant secondary device through a communication connection outside the bus; and Transmitting status information indicating that the one of the main redundant device or the redundant secondary device operating in the active mode is about to become inoperative or inoperable from that of the main redundant device or the redundant secondary device operating in the active mode, to the other of the main redundant device or the redundant secondary device via the communication link. A method of implementing redundant devices within a process control system in a process control network according to claim 16, characterized by storing messages received over the bus in the subscriber buffer of the redundant secondary device. A method of implementing redundant devices within a process control system in a process control network according to any one of claims 16 to 21, further comprising: Configuring the redundant master and the redundant secondary to process messages having the unique address of at least one device; Receiving the messages having the unique address of the at least one device; and Processing the messages having the unique address of the at least one device in the main redundant device and the redundant secondary device while operating in the active mode and the backup mode. A method of implementing redundant devices within a process control system in a process control network according to any one of claims 16 to 22, characterized in that the bus has a first portion and a second portion, the first and second portions each communicating at least one of them with the bus wherein the method further comprises establishing a communication connection between the main redundant device and the redundant secondary device parallel to each other and in series between the first section and the second section of the bus. A method of implementing redundant devices within a process control system in a process control network as recited in any of claims 16 to 23, further comprising establishing a communication connection between the main redundant device and the redundant secondary device through a communication link outside the bus. A method of implementing redundant devices within a process control system in a process control network according to any one of claims 16 to 24, further comprising: Configuring the redundant main device and the redundant secondary device to detect the connection of the other of the redundant main device and the redundant secondary device, respectively; Detecting at the redundant main device the connection of the redundant secondary device and at the redundant secondary device the connection of the redundant main device; Causing the redundant master to operate in the active mode based on the connection of the redundant secondary device; and Causing the redundant secondary to operate in the spare mode based on the connection of the redundant main. A method of implementing redundant devices within a process control system in a process control network according to any of claims 16 to 25, wherein the devices are in communication with the bus via slots, the method further comprising: Establishing a communication connection between the redundant main device and the bus via a first slot; Establishing a communication link between the redundant secondary device and the bus via a second slot; Causing the redundant master to establish communication with the bus via the first slot and to operate in the active mode based on the determination that the redundant host is connected to the bus via the first slot; and Causing the redundant secondary to determine the connection to the bus via the second slot and to operate in the spare mode based on the determination that the redundant secondary is connected to the bus via the second slot. A method of implementing redundant devices within a process control system in a process control network as recited in claim 26, wherein each of the first and second slots has a plurality of contact pins connecting the first and second redundant devices to the first and second slots, respectively each pin has an associated voltage level, the method further comprising: Determining, based on the voltage levels of the contact pins of the first slot, that the redundant main device is connected to the bus via the first slot; and Determining, based on the voltage levels of the contact pins of the second slot, that the redundant secondary device is connected to the bus via the second slot. A method of implementing redundant devices within a process control system in a process control network according to any of claims 16 to 27, wherein a host device having an indication is in communication with the bus, the method further comprising: Detecting the presence of the redundant master and the redundant secondary, the operation of the redundant master in the active mode, and the operation of the redundant secondary in the backup mode in the host device; and Indications on the display of the host device of indications of the presence of the redundant main device and the redundant secondary device, the operation of the redundant main device in the active mode and the operation of the redundant secondary device in the reserve mode. A method of implementing redundant devices within a process control system in a process control network according to any one of claims 16 to 28, characterized in that the publication virtual address is one of the first unique address and the second unique address. Method for implementing redundant devices within a process control system in a process control network according to one of Claims 16 to 29, characterized in that the main redundant device and the redundant secondary device are I / O devices. Redundant device pair of a virtual I / O device ( 130 ) in a process control network having a plurality of devices communicatively connected via a bus, each of the plurality of devices having a unique address and being capable of communicating over the bus, at least one of the plurality of devices so programmed is that she is on the Bus published messages having a virtual publication address, the redundant device pair comprising: a redundant main device ( 120 ) of the virtual I / O device ( 130 ) with a first unique address associated with the bus ( 110 ) is communicatively connected and programmed to publish messages on the bus having the virtual publication address and a publication buffer ( 132 ) and a participant buffer ( 134 ); and a redundant secondary device ( 122 ) of the virtual I / O device ( 130 ) having a second unique address communicatively coupled to the bus and programmed to publish messages on the bus having the virtual publication address and a publication buffer ( 136 ) and a participant buffer ( 138 ); wherein the redundant main device operates in an active mode in which the redundant main device transmits messages for at least one of the plurality of devices on the bus, and the redundant secondary device operates in a back-up mode in which the secondary device does not transmit messages on the bus; where the publication buffer ( 136 ) of secondary equipment ( 122 ) messages received in the reserve mode from the main facility ( 120 ) stores. A redundant device pair according to claim 31, characterized in that the redundant secondary means operates in the active mode when the redundant main means is inoperative. A redundant device pair according to claim 31 or 32, characterized in that said redundant secondary means determines that said redundant main device is inoperative when said redundant main device does not transmit messages on said bus having said virtual publication address. A redundant device pair according to any one of claims 31 to 33, further comprising a controller communicatively coupled to the main redundant device and the redundant secondary device and programmed to receive status information from the main redundant device and the redundant secondary device and upon receipt of status information, indicating that the redundant master is about to become inoperative or inoperative, causing the redundant master to operate in stand-by mode, and the redundant secondary to operate in active mode. Redundant device pair according to one of Claims 31 to 34, characterized in that the redundant main device and the redundant secondary device are connected by a communication link ( 140 ) are communicatively coupled to each other outside the bus and the redundant master device is programmed to provide status information indicating that the redundant master is about to become inoperable or inoperable to the redundant secondary device via the communications link (5). 140 ) transmits. Redundant device pair according to claim 31, characterized in that the publication buffer of the redundant secondary device stores in reserve mode via a bus received messages of the redundant main device. A redundant device pair according to any one of claims 31 to 36, characterized in that the main redundant device and the redundant secondary device are programmed to process messages having the unique address of at least one device, and the redundant main device and the redundant secondary device receive messages and process having the unique address of at least one device while operating in the active mode and in the spare mode. Redundant device pair according to one of Claims 31 to 37, characterized in that the bus ( 110 a first portion and a second portion, the first and second portions each having at least one communicating means in communication therewith, the redundant main and redundant secondary means being parallel to each other and in series between the first portion and the second portion of the first portion Buses ( 110 ) are connected in communication connection. Redundant device pair according to one of Claims 31 to 38, characterized in that the redundant main device and the redundant secondary device are connected by a communication link ( 140 ) outside the bus ( 110 ) are communicatively connected with each other. A redundant device pair according to any one of claims 31 to 39, characterized in that the redundant main device and the redundant secondary device are configured to detect the presence of each of the other redundant main device and redundant secondary device and determine which of the redundant main device and the redundant secondary device in the active mode will work and which will work in reserve mode. Redundant device pair according to one of Claims 31 to 40, characterized in that the redundant main device ( 120 ) by bus ( 110 ) via a first slot ( 156 ) is in communication connection and the redundant secondary device ( 122 ) by bus ( 110 ) via a second slot ( 157 ), wherein the redundant main device and the redundant secondary device are configured to be based on the determination that the redundant main device is connected to the first slot (12). 156 ) determines that the redundant main device is connected to the first slot ( 156 ) and operates in the active mode, and based on the determination that the redundant secondary device (16) 122 ) with the second slot ( 157 ) determines that the redundant secondary device is connected to the second slot ( 157 ) and works in the reserve mode. A redundant device pair according to claim 41, characterized in that said first and second slots each comprise a plurality of pins connecting said first and second redundant means respectively to said first and second slots, each pin having an associated voltage level the redundant main device and the redundant secondary device determine that the redundant main device with the first slot ( 156 ) and the redundant secondary device with the second slot ( 157 ), based on the voltage levels of the contact pins. A redundant device pair according to claim 31, characterized in that the virtual publication address is one of the first unique address and the second unique address. Redundant device pair according to claim 31, characterized in that the redundant main device and the redundant secondary device are I / O devices. Redundant device pair according to claim 31, characterized in that the redundant secondary device ( 122 ) is in reserve mode for processing the messages received over the bus and is for publishing the virtual publication address of the virtual device. Redundant device pair according to claim 31, characterized in that the redundant secondary device ( 122 ) in the reserve mode for maintaining the data provided by the redundant main facility ( 120 ) constructed communication connection is formed.

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